Pneumatic classifier with particle removal system

Abstract

An apparatus for pneumatically classifying non-uniform materials such as mineral particles and mine run materials which contain sizes ranging from relatively course particles down to fine dust. The apparatus includes a closed housing wherein a controlled air flow rapidly and efficiently classifies large quantities of material which pass through various classifying stages. The housing is provided with a system to remove and collect fines or dust from the housing which are created during the classifying operation on many types of material. The removal and collection system functions to withdraw a portion of the flow circulating in the housing and through the operation of a precipitator removes fines for collection whereby particle free air is returned to the controlled flow without disturbance to the classifying process.

What is claimed is: 
     
       1. A pneumatic classifier comprising: feed means for creating a stream of solid material having particles of varying sizes;   classifying means responsive to air flow for receiving said stream to classify the particles into fractions containing substantially uniform sizes;   air flow means operatively coupled to the classifying means to create a controlled air flow for contacting the stream to effect classification of a substantial portion of the particles into fractions;   particle collection means operatively mounted adjacent the classifying means to collect unclassified particles of the stream other than said substantial portion which unclassified particles remain in said controlled air flow after passing through the classifying means;   said particle collection means including particle removal means in fluid communication with an inlet means and an outlet means, said inlet means being mounted adjacent said controlled air flow means for extracting a portion of the controlled air flow having unclassified particles to be collected and said outlet means mounted downstream of said particle removal means for returning particle free air to the controlled air flow without disturbance thereto;   said particle removal means including means for creating a secondary air flow between said inlet means and said outlet means; and   housing means for confining the controlled air flow created by said air flow means into a confined circulating flow through said classifying means, said inlet means and said outlet means extending substantially the width of the controlled air flow in said housing means.   
     
     
       2. A pneumatic classifier as claimed in claim 1, wherein said outlet means includes a hood having an angularly disposed portion to direct the particle free air back into the classifying means. 
     
     
       3. A pneumatic classifier comprising: feed means for creating a stream of solid material having particles of varying sizes;   classifying means responsive to air flow for receiving said stream to classify the particles into fractions containing substantially uniform sizes;   air flow means operatively coupled to the classifying means to create a controlled air flow for contacting the stream to effect classification of a substantial portion of the particles into fractions;   particle collection means operatively mounted adjacent the classifying means to collect unclassified particles of the stream other than said substantial portion which unclassified particles remain in said controlled air flow after passing through the classifying means;   said particle collection means including particle removal means having inlet means for extracting a portion of the controlled air flow having unclassified particles to be collected and outlet means for returning particle free air to the controlled air flow without disturbance thereto;   said particle removal means including means for creating a secondary air flow between inlet means and said outlet means;   housing means for confining the controlled air flow created by said air flow means into a confined circulating flow through said classifying means; and   said housing means including a housing having an upper portion and a curved wall disposed in the upper portion to concentrate the unclassified particles thereto, said inlet means including a cut gate having a curved surface extending within the controlled air flow in the upper portion of the housing.   
     
     
       4. The classifier of claim 3 wherein said air flow deflects the particles on contact to classify the particles in fractions containing substantially uniform sizes. 
     
     
       5. The classifier of claim 4 wherein said feed means creates a stream of freely falling solid material. 
     
     
       6. The classifier of claim 1 in which the particle removal means induces swirling flow within a chamber having a cylindrical inner wall. 
     
     
       7. The classifier of claim 6 wherein the air flow laden with a mass of unclassified material enters the chamber adjacent one end thereof and further including means mounted adjacent the opposite end to receive the mass separated from the air flow. 
     
     
       8. The classifier of claim 7 further including outlet means extending within the chamber to receive air flow having the mass of unclassified material separated therefrom. 
     
     
       9. The classifier of claim 8 wherein said unclassified material collects beneath said outlet.